Ohi H et al. (2003), Molecular cloning and expression analysis of th...

XB-ART-4918

Biochem Biophys Res Commun 2003 Aug 01;3073:595-9. doi: 10.1016/s0006-291x(03)01244-0.

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Molecular cloning and expression analysis of the aryl hydrocarbon receptor of Xenopus laevis.

Ohi H , Fujita Y , Miyao M , Saguchi K , Murayama N , Higuchi S .

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The aryl hydrocarbon receptor (AHR) is a member of the basic helix-loop-helix/Per-Arnt-Sim (bHLH/PAS) family of transcription factors. Although this receptor has been known to mediate the toxic effects of environmental pollutants, its physiological functions remain elusive. Here, we describe the isolation and expression pattern of the Xenopus AHR gene. The predicted amino acid sequence contained regions characteristic of other vertebrate AHRs. However, in line with previously described fish AHR genes, no distinct Q-rich domain was found. Phylogenetic analysis demonstrated that Xenopus AHR was clustered within the AHR1 clade. As in the case of mammalian AHR genes, the Xenopus AHR gene was expressed in all the adult tissues tested. Xenopus AHR was also expressed during early development, in parallel with expression of the CYP1A7 gene, which is thought to be regulated by AHR. These results suggest that while frogs are relatively tolerant to TCDD toxicity, the AHR of frogs has characteristics similar to those of other vertebrate AHRs.

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Species referenced: Xenopus laevis
Genes referenced: ahr arnt

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	Fig. 1. Deduced amino acid sequence of Xenopus AHR and alignment with human AHR (GenBank Accession No. P35869), mouse AHR (AAL89735), Fundulus AHR1( AAC60334), and AHR2 (AAC59696). Amino acid residues conserved in at least four sequences are boxed. Solid lines indicate the basic, HLH, PAS A, and PAS B domains in the sequences.
	Fig. 2. Phylogenetic analysis of AHR amino acid sequences. The GenBank accession numbers of the AHR sequences used are: human (P35869), rat (P41738), mouse (AAL89735), chicken (AF192502), Fundulus AHR1( AAC60334) and AHR2 (AAC59696), rainbow trout AHR2a (AF065137) and AHR2b (AF065138), clam (AAF70378), Drosophila spineless (AAD09205), and C. elegans (AF039570).
	Fig. 3. RT-PCR analysis of Xenopus AHR expression in various tissues from an adult individual. Total RNA was isolated from 10 tissues and reverse-transcribed as described under Materials and methods. L8 levels are shown for comparison.
	Fig. 4. Temporal expression of Xenopus AHR transcripts during early development analyzed by RT-PCR. Stages of RNA preparation are indicated above each column. ODC levels are shown for comparison. UF: unfertilized eggs.